1. Field
Example embodiments relate to semiconductor memory devices, for example, to resistive random access memory devices and/or example methods of manufacturing the same.
2. Description of the Related Art
Related art resistive random access memory (RRAM) may use a resistance change material, such as a transition metal oxide, with a resistance that may change according to applied voltage. If a voltage equal to or higher than a set voltage is applied to a resistance change material, resistance of a resistance change material may decrease, and this state may be referred to as an ON state. If a voltage equal to or higher than a reset voltage is applied to a resistance change material, the resistance of the resistance change material may increase, and this state may be called an OFF state.
Related art RRAMs may have an operating speed that is about 105 times faster than flash memories and may have other advantages such as being capable of lower voltage driving. Related art RRAMs may allow for more than about 1010 instances of repetitive writing and/or erasing, and thus may be expected to be used in many apparatuses that may require a storage unit.
Related art RRAMs may store a 0 or 1 in a unit cell, and may not store multi-bit data. Integration of related art RRAMs may not increase by the use of multi-bit data.